Conventionally, a controller has been known in which an operating voltage at which the power of an electrical generator is maximum is determined as a voltage by a primary search operation, a search is performed by stepwise variation of the operating voltage with a primary operating voltage as a reference, and the operating voltage at which the electrical power is maximum is determined as a secondary search operating voltage. In this apparatus, because the operating voltage is searched for based on information of an electrical generator controlled by the apparatus itself, there has been a case in which it is not possible to appropriately set the search timing for the operating point.